The present invention relates to a method for cutting sheets and to a sheet processing machine. A trailing end of a sheet is cut perpendicularly to a sheet transport direction by a first transverse cutting device. The sheet is then rotated or turned and the now trailing end is cut by a second transverse cutting device.
DE-AS 10 44 589 describes a transverse cutting device for paper webs. A belt system for transporting the sheets cut from the web is connected downstream of the transverse cutting device.
DE 43 13 452 A1 describes a device for cutting sheets from a web. Two transverse cutting mechanisms are provided with this device, by means of which first a leading end of the web is exactly cut to measure and the sheet is then cut off the web.
DE 42 38 387 A1 discloses a cut registration regulating device on transverse cutters of rotary printing presses. Here, a rotating cylinder is provided, which works together with a stationary opposed cutter.
The object of the present invention is based on creating a method for cutting sheets, and on a sheet processing machine with a cutting device.
In accordance with the invention, this object is attained by providing a sheet processing machine which initially trims a trailing end of a sheet perpendicularly to a sheet transport direction by use of a first transverse cutting device. The sheet is then turned so that the trimmed trailing end now leads. The now trailing end of the sheet is trimmed perpendicularly to the sheet transport direction by a second transverse cutting device.
The advantages which can be achieved by means of the present invention lie, in particular, in that transverse cutting from the start to the end of a sheet takes place without manual intervention in a sheet processing machine. It is possible, by means of integrated inspection devices, to control the print quality itself, as well as the cut registrations in the sheet processing machine. In this way, it is possible to simultaneously control the fronts and backs of the sheet, which were printed, for example, on the obverse and reverse sides of the sheet.
A simple cut registration adjustment is possible because of the working together of the transverse cutting devices with a chain conveyor. This adjustment is advantageously performed by means of a position-controlled electric motor driving a cutting cylinder.
A longitudinal cutting device is assigned to a processing cylinder of the sheet processing machine, so that the sheet is cut xe2x80x9cin-linexe2x80x9d into two or more partial sheets. These sheets can be deposited on stacks, which can be selected by means of the inspection device. In this manner, sorted stacks with xe2x80x9cgoodxe2x80x9d and with waste sheets are formed. This has the advantage that, in case of a defective partial sheet, the entire sheet is not wasted.
By means of this sheet processing machine all sides of a sheet are cut and the latter is cut into partial sheets. All cuts made, as well as the obverse and reverse printing, are controlled by means of inspection devices. All of the cut sheets are deposited on selectable stacks.
This sheet processing machine performs a plurality of processing steps xe2x80x9cin-linexe2x80x9d, which leads to an increase in production and also to a reduction of manual labor. Moreover, the quality of the products made in this way is increased.